nextjs - 💡(How to fix) Fix Parallel routes breaks typed routes [1 comments, 2 participants]

nextjs2026-02-16 18:33:02

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vercel/next.js#90055•Fetched 2026-04-08 00:20:54

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mordechaim

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mordechaim

Osamor-Chukwuka

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Error Message

Likewise, building the project fails with the same error because it runs the TypeScript compiler. .next/dev/types/app/@sidebar/layout.ts:36:13 - error TS2344: Type 'OmitWithTag<{ params: Promise<{}>; children: ReactNode; } & { sidebar: ReactNode; }, keyof LayoutProps, "default">' does not satisfy the constraint '{ [x: string]: never; }'. Found 1 error in .next/dev/types/app/@sidebar/layout.ts:36 This error is unique to the Webpack build chain. On Turbopack I did not observe this error. This error is present on both latest and canary. But on canary but I ran into a additional TypeScript error, which effects both Webpack and Turbopack and is present even without parallel routes: .next/dev/types/validator.ts:5:56 - error TS2307: Cannot find module './routes.js' or its corresponding type declarations.

Root Cause

Likewise, building the project fails with the same error because it runs the TypeScript compiler.

Code Example

.next/dev/types/app/@sidebar/layout.ts:36:13 - error TS2344: Type 'OmitWithTag<{ params: Promise<{}>; children: ReactNode; } & { sidebar: ReactNode; }, keyof LayoutProps, "default">' does not satisfy the constraint '{ [x: string]: never; }'.
  Property 'sidebar' is incompatible with index signature.
    Type 'ReactNode' is not assignable to type 'never'.
      Type 'undefined' is not assignable to type 'never'.

36 checkFields<Diff<LayoutProps, FirstArg<TEntry['default']>, 'default'>>()
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Found 1 error in .next/dev/types/app/@sidebar/layout.ts:36

---

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32189
  Available CPU cores: 14
Binaries:
  Node: 25.0.0
  npm: 11.6.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.1.6 // Latest available version is detected (16.1.6).
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: N/A

---

.next/dev/types/validator.ts:5:56 - error TS2307: Cannot find module './routes.js' or its corresponding type declarations.

5 import type { AppRoutes, LayoutRoutes, ParamMap } from "./routes.js"
                                                         ~~~~~~~~~~~~~

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Link to the code that reproduces this issue

https://github.com/mordechaim/parallel-typed-routes

To Reproduce

Start the dev server
Load the page (this triggers typed routes generation)
Run the types script

Likewise, building the project fails with the same error because it runs the TypeScript compiler.

Current vs. Expected behavior

Typescript errors with the following:

.next/dev/types/app/@sidebar/layout.ts:36:13 - error TS2344: Type 'OmitWithTag<{ params: Promise<{}>; children: ReactNode; } & { sidebar: ReactNode; }, keyof LayoutProps, "default">' does not satisfy the constraint '{ [x: string]: never; }'.
  Property 'sidebar' is incompatible with index signature.
    Type 'ReactNode' is not assignable to type 'never'.
      Type 'undefined' is not assignable to type 'never'.

36 checkFields<Diff<LayoutProps, FirstArg<TEntry['default']>, 'default'>>()
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Found 1 error in .next/dev/types/app/@sidebar/layout.ts:36

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32189
  Available CPU cores: 14
Binaries:
  Node: 25.0.0
  npm: 11.6.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.1.6 // Latest available version is detected (16.1.6).
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Parallel & Intercepting Routes, TypeScript, Webpack

Which stage(s) are affected? (Select all that apply)

next dev (local), next build (local)

Additional context

Removing /@sidebar/layout.tsx causes this issue to go away.

This error is unique to the Webpack build chain. On Turbopack I did not observe this error.

This error is present on both latest and canary. But on canary but I ran into a additional TypeScript error, which effects both Webpack and Turbopack and is present even without parallel routes:

.next/dev/types/validator.ts:5:56 - error TS2307: Cannot find module './routes.js' or its corresponding type declarations.

5 import type { AppRoutes, LayoutRoutes, ParamMap } from "./routes.js"
                                                         ~~~~~~~~~~~~~

extent analysis

Quick Fix Overview

Relax the “no‑extra‑keys” constraint that checkFields enforces – allow layout components to expose extra props (e.g. sidebar).
Update the utility type OmitWithTag (or the checkFields signature) so it no longer resolves to { [x: string]: never }.
Fix the missing‑module error by either:
- adding the .js extension to the import or
- enabling the new “bundler” module‑resolution mode in tsconfig.json.

Below are the concrete code changes and the exact steps to get the project compiling again.

1️⃣ Relax the `checkFields` constraint

File: src/types/checkFields.ts (or wherever checkFields is declared)

// Old signature (simplified)
export function checkFields<T extends { [K in keyof T

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nextjs - 💡(How to fix) Fix Parallel routes breaks typed routes [1 comments, 2 participants]

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Error Message

Root Cause

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Quick Fix Overview

1️⃣ Relax the `checkFields` constraint

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nextjs - 💡(How to fix) Fix Parallel routes breaks typed routes [1 comments, 2 participants]

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GitHub issue graph ai analysis

Error Message

Root Cause

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Quick Fix Overview

1️⃣ Relax the checkFields constraint

Still need to ship something?

RELATED_DISCOVERY

TRENDING

1️⃣ Relax the `checkFields` constraint